1. Field of the Invention
The present invention concerns a capacitor element with patterned electrode-areas for capacitive measuring devices.
More particularly, the present invention concerns a capacitor element with patterned electrode areas for capacitive measuring devices, with mutually displaceable capacitor parts to vary the capacitance of the measuring device as a function of the relative positions of the capacitor parts, wherein a plurality of individual electrode areas are arranged on a first side of an insulating substrate and conducting strips electrically connecting these areas to each other and to terminals being disposed on a second side of the substrate.
2. Description of the Prior Art
Applications are known wherein capacitive measuring devices with mutually rotating capacitor parts are used for measuring rotation. Again, capacitive measuring devices are known to be used for linear applications where the parts of a capacitor are displaced linearly relative to each other. The accuracy of measurement and/or resolution of such angular and linear measuring devices within their measuring range essentially depends on the fineness of the graduation of the capacities of these measuring elements. This means that, for a measuring device for angles with electrode-areas in the form of circle-sectors, the resolution of the measurable angular difference improves as more sectors are defined on the measuring device, i.e. with an increase in the number of sector electrode-areas on its capacitive element. In identical manner, as regards linear measuring devices for measuring lengths, the resolution of the measurable differences in distance is higher with an increase in the number of electrode-areas per unit length on the capacitive element.
The individual electrode-areas must be connected electrically to each other and to the electronic circuit analyzing the capacitance of the measuring device corresponding to an arbitrary position of its capacitive elements, so that each electrode area is provided with at least one contact point. Such connections ordinarily are arranged on the back side of the capacitor element, due to the arrangement and geometry of the electrode areas. Conventionally, the contacts are implemented by boreholes or apertures passing through the electrode areas and the substrate bearing said areas, whereby the electrode areas are contacted on the back side of the capacitor element. The size and the position of these boreholes or apertures not only affect the capacitance of every electrode area, if arranged in the active capacitor zone, but also essentially defines the minimum dimensions of the electrode areas. In practice this makes it difficult to manufacture capacitor elements with sector electrode-area patterns of small diameters which contain a large number of such sector electrode-areas. For the same reasons, even linear capacitive measuring devices require minimal widths for the electrode areas, to reliably overlap the contact-holes in the substrate. That means that the resolution of rotational and linear motion is limited considerably, because relatively large mechanical motions are required to change the capacitance of the measuring device. It is obvious that, especially in high precision measurements, the above conditions represent a drawback.